Renal Embryology Flashcards
Three Kidney Systems
Derived from intermed mesoderm
Pronephros
Only appear in week 4
Cervical & upper thoraci region
Segmented
Form vesitigial excretory units- nephrotomes
Regress by end of 4th week- non f
mesonephros
Unsegmented mesonephros- nephrogenic cord
mesonephric (wolffin) ducts- from upper thoracic to upper lumbar L3 segments
Early in 4th week
Excretory tubules derived from unsegmented mesonephros
Week 7- baby produces urine, cloacal mem ruptures, pee comes out of membrane into amniotic cavity, baby swallows its own pee with amniotic fluid
By 2nd month- mesonephros & mesnephric ducts disappear
In males, part of caudal tubules & mesonephric ducts remain & participate as vas deferns (part of it)
Metanephros
Definitive kidney
Appears in week 5, nephros develop from metanephric mesoderm
Permanent Kidney
2 origins:
metanephros- 3rd kidney sys, excretory unit (Bowman’s capusle, PCT, loop of Henle, DCT)
mesoneprhos- uteric bud, collecting sys (collecting tubule, duct, minor & major calyces, renal pelvis, ureter)
Uteric Bud
Outgrwoth of mesnephric duct
Primordium of collecting sys (collecting tubule–> ureter)
Early 5th week
3rd kidney system!
Collecting Sys
From ureter to collecting tubules
Mesonephric origin (ureteric bud)
Bowman’s capsule to DCT
Metanephric origin:
- ureteric buds continue to bifurcate until 32nd week, produce 1-3 million collecting tubules
- tip of ea collecting tubule induces dev of metanephric tissues cap, continues to lengthen to form Bowman’s capusle to DCT
- metanephric tissue= surrounds collecting tubule & duct
Final Kidney
Definitive kidney created b/t 5-15 week
Urine produced by kidnye passed into amniotic cavity in 12th week
During fetal life, kidneys NOT RESPONSIBLE for waste excretion.
Reciprocal induction b/t metanephric mesenchyme & ureteric bud
WT1; expressed by mesenchye, TF that makes this tissue competent to respond to induction by ureteric bud
no WT1= no kidney
Wilm’s Tumor/ nephroblastoma
WT1 mutation, rapidly form malignancy
<5 yo
WAGR Syndrome
Wilm’s tumor
Aniridia (no iris in eye)
Genitourinary anomalies
Mental retardation
Hemihyperthrophy
Chome 11 deletion
Obesity
Multicystic Dysplastic Kidney
Nephrones fails to dev, collecting duct never forms
1/2400
Renal Agenesis
No kidney
Ureteric bud fails to contact & induce metanephric mesenchyme
U/L: 1/1000, usually male, asymptomatic
B/L: char facial appearance & oligohydramnios
Potter Seq
typical appearance of fetus or neonate due to oligohydramnios in utero
Lack of kidney, anuria, oligohydramnios (low volume of amniotic fluid), hypoplastic lungs; other abnormalities (under dev lungs, club foot etc. )
Congenital Polycystic Kidney CPK
Numerous cysts formed in kidney, autosomal trait
Auto recessive PK= progressive, cysts form from collecting ducts, infancy or childhood renal failure
Autosomal dominant CPK= less progressive, cysts form from all segments of nephron, adult renal failure
Duplication of Ureter
Early splitting of ureteric buds
Ectopic ureter
Dev of 2 ureteric buds
One normal & other moves down with mesonephric duct
Entrance in bladderm urethra, vagina
Embryonic Origin
A= PCT; 3rd kidney sys (metonephros)
B= thin limb, 3rd (metonephros)
D= collecting duct, 2nd (ureteric bud(
Kidney Position
Ascend from their original region (sacral) to lumbar site.
Definitive position is attained by 9th week
Abnormal Kidney Location
Pelvic kidney- asymptomatic
Horeshoe kidney- ascent of kidneys prevetned by IMA, asymptomatic but Wilm’s tumor occurs more frequently
Bladder & Urethra
From cloaca
During 4-7th week, cloaca divided by urorectal septum into rectoanal canal (post)
primitive urogenital sinus (und)
Bladder
Prostatic & membranous urethra
Definitive urogenital sinus- vestibule of vagina or penile urethra
Bladder Formation
Majority of bladder- primitive urogenital sinus (endoderm)
Trigone- mesonephros (intermed mesoderm)
End 3rd Month
Outgrowth from urethra:
male- prostate gland
female- urethral glands & paraurethral glands
Budding from ductus deferens- seminal vesicles
Bladder Defects
Due to allantois persisting
Exstrophy of bladder
Rare
Ventral body wall defects
Constant associated with epispadias (urethra plate of deep red mucosa lying on dorsal penis)
Ant urinary bladder wall break down & expose mucosa of post bladder
Exstrophy of cloaca
Rare
More severe ventral body wall defect
Migration of mesoderm to midline inhibited
Exstrophy of bladder, spinal defects, imperformate anus, omphalocele
